Prompt Modal Types

Window Prompts

Window prompts are system prompts. They are clearly distinguishable from website content and can be opened with or without a parent window. While a window prompt is open, the parent window cannot be interacted with. That means the user can not close the window or switch tabs. Providing a parent window is optional, but highly encouraged. If you do not pass a parent the implementation will try to find one or fallback to aborted standalone window.

When to use: This should be reserved for important browser-wide messages with the intent to block any further user interaction until the message has been read.



When using window prompts, make sure they can not be spawned by web content. We’ve seen cases of DoS attacks in the wild where websites spammed window prompts to lock up the browser. This prompt type should only be used when necessary and with proper rate limiting. Most of the time, a tab prompt can be be used.

Screenshot of a window prompt.

Window alert prompt

Tab Prompts

Tab prompts are system prompts like window prompts. As opposed to window prompts, they are tab modal and don’t steal focus from the parent window. Multiple tab prompts cannot be shown at the same time. When opening additional prompts, they are FIFO queued.

When the user closes the tab or navigates to a different URI, prompts associated with the given tab are closed. In this case an exception will be thrown:

Exception: prompt aborted by user

When to use: This prompt should be used for dialogs that were caused by web content and thus should be bound to the scope and lifetime of a specific tab, but should still look like secure browser UI. Examples are HTTP Auth prompt or the dialog to add a new search provider for the current website.


Screenshot of a tab prompt.

Tab alert prompt

Content Prompts

Content prompts are like tab prompts, but they belong to the web content. Thus, they are positioned in the center of the selected browser.

When to use: The prompt is triggered by or as a result of an action of web content and is not intended to look like secure browser UI.


Screenshot of a content prompt.

Content alert prompt

Disabling tab/content modal prompts

You can disable tab and content modal prompts and get back window-modal for individual prompts by setting the prompts.modalType.<promptName> preference to 3.